This invention relates generally to gas turbine engines and more particularly to combustors for gas turbine engines that have can type combustion liners.
Allison Gas Turbine Division of General Motors Corporation presently produces a state-of-the-art combustor that comprises six circumferentially spaced can type combustion liners located in an annulus formed by inner and outer engine casings. Cross over tubes interconnect the combustion liners and provide flame transfer for starting the engine. Each combustion liner has a fuel nozzle that is connected to a fuel manifold attached to an external surface of the outer engine casing.
While these gas turbine engines perform very well, new stricter air quality control regulations require significant reductions in emissions of oxides of nitrogen (NOx). At the same time emissions of carbon monoxide (CO) and unburned hydrocarbons (UHC) must be maintained at low levels.
A common way to reduce NOx emission is to inject water or steam into the combustor. However, water or steam injection generally results in increased emissions of carbon monoxide and unburned hydrocarbons. Moreover such system are costly from both installation and operational standpoints.